Carburetor/crankcase Pressure Gauge

Detects leaks on carburetor in seconds
Hold a 4 cycle carburetor upside down in your hand and pump to 5 psi and see if the gauge holds and doesn't leak off. If it holds, the needle and seat are working and not leaking off.
For a 2 cycle carburetor and pump to 5 psi and see if it holds. If it does, the needle is working.